PSI - Issue 2_A

Morozov V.A. et al. / Procedia Structural Integrity 2 (2016) 1002–1006 Author name / Structural Integrity Procedia 00 (2016) 000–000

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high strain rates. The subject of this work is to develop a method of loading and deformation of the ring samples using electric explosion of conductors and carrying out structural analysis of the fracture surfaces. Conductor is placed in the elastomer of cylindrical shape, which is then evaporated during the passage of electric current from the charger through conductor in wire explosion technique. The energy of the expanding plasma is transmitted to ring sample through the elastomer, in which cylindrical shock wave is formed. In this loading method, the complexity is to determine the radial pressure on the inner surface of the ring. In this paper, this difficulty is overcome by measuring the specified pressure using a specially designed piezosensor. A limitation of this method is the life time of elastomer, i.e. it is destroyed under the electric explosion of conductor. For this purpose, an elastomer material was selected that it could withstand multiple exposures. Three materials were chosen: caprolactan, fluoroplastic and polymethyl methacrylate (PMMA). The most perspective material turned out to be fluoroplastic.

Nomenclature L

distance from the cylinder axis, mm radial pressure in the elastomer, MPa circumferential stress in the elastomer, MPa circumferential pressure in the ring, MPa

P re σ ce P cr

dε/dt

strain rate, 10 4 , 1/s

δ Al

elongation of aluminum ring after testing, %

Shear % fiber on the fracture surface, % S aluminum sample cross-section, mm 2 D g grain size, μm HV microhardness, MPa

2. Materials and experimental technique The aluminum rings of varying thickness and widths were used as test samples.

The experiments were performed on the generator of short voltage pulses that provides the formation of electrical voltage with amplitudes (10-22) Kv. Fig. 1 shows an electrical circuit of sample loading. Capacity of charged capacitor was 0.5 microfarads.

Fig. 1. Installation scheme: 1 - auto-transformer; 2 - the rectifier; 3 - charger resistance; 4 - capacitor; 5 - discharger; 6 - Rogowski coil; 7 - blasted conductor; 8 - elastomer; 9 - Oscilloscope; 10 - ring sample.